Flexible Soft Wipe Comprising Individualized Bast Fibers

ABSTRACT

The present invention relates to a nonwoven substrate comprising individualized flax fibers comprising specific cellulose, hemicellulose and lignin contents.

TECHNICAL FIELD

The subject of the invention is a nonwoven substrate comprising wood fibers and individualized bast fibers.

PRIOR ART

Disposable wipes are conventionally composed of non-biodegradable plastic fibers such as, for example, polyester fibers and thermoplastic fibers. Conventional disposable wipes are rarely recycled by users. Conventional disposable wipes therefore have a considerable environmental impact because of the long plastic fibers that they contain.

In order to limit the environmental impact of disposable wipes, it has been proposed to replace the synthetic or artificial fibers with bast fibers. However, these wipes are rough and are not sufficiently flexible to easily conform to the face of the users of cosmetic wipes. The sensations that they provided to the users are therefore not satisfactory. Furthermore, these wipes are difficult to produce because bast fibers are naturally rigid and very barely flexible.

Technical Problem

There is therefore a need for a wipe which is flexible, which is pleasant to the touch, and which is easy to produce.

It is thus to the credit of the inventors to have found that it is possible to meet this need by virtue of individualized bast fibers that are easy to produce and characterized by specific cellulose, lignin and hemicellulose contents.

SUMMARY

It is proposed a nonwoven substrate comprising:

-   -   from 40% to 95% of wood fibers by weight relative to the total         weight of fibers of the substrate, and     -   from 5% to 60% of individualized bast fibers by weight relative         to the total weight of fibers of the substrate,         characterized in that the individualized bast fibers have,         relative to the dry weight of the individualized bast fibers, a         cellulose content greater than or equal to 75%, a hemicellulose         content less than or equal to 10%, and a lignin content less         than or equal to 7%.

Advantageously, the nonwoven substrate of the invention is pleasant to the touch, is flexible, has a natural color and has mechanical properties, in particular dry and wet tensile strengths, of the same order of magnitude as a nonwoven substrate not comprising individualized bast fibers.

According to another aspect, it is proposed a process for producing the nonwoven substrate of the invention, the process comprising the following steps:

-   -   a) treating bast fibers under pressure in a solvent in order to         obtain the individualized bast fibers,     -   b) mixing the individualized bast fibers and wood fibers in         order to obtain a fiber mixture, and     -   c) producing a nonwoven substrate from the fiber mixture by the         wetlaid process, by the drylaid process or by the airlaid         process, in particular by the wetlaid process.

The treatment step a) of the process of the invention advantageously makes it possible to simply obtain the individualized bast fibers having the particular cellulose, hemicellulose and lignin contents. This extraction step a) therefore makes it possible to simply produce a flexible nonwoven substrate which is pleasant to the touch and which has mechanical properties of the same order of magnitude as a nonwoven substrate comprising bast fibers that have not been chemically treated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a microscopy image of flax fibers having undergone a treatment under pressure according to the invention.

FIG. 2 shows a microscopy image of flax fibers having undergone a treatment under pressure according to the invention.

FIG. 3 shows a microscopy image of flax fibers having undergone a treatment under pressure according to the invention.

FIG. 4 shows a microscopy image of flax fibers having undergone a treatment under pressure according to the invention.

FIG. 5 shows a microscopy image of flax fibers having undergone a treatment under pressure according to the invention.

FIG. 6 shows a microscopy image of flax fibers having undergone a comparative treatment.

FIG. 7 shows a diagram of the dry tensile strengths of a control substrate, a comparative substrate and substrates of the invention.

FIG. 8 shows a diagram of the deformation at break of a control substrate, a comparative substrate and substrates of the invention.

FIG. 9 shows an optical microscopy image of a substrate according to the invention (optical zoom ×200, the two circles are added).

FIG. 10 shows an optical microscopy image of a comparative substrate (optical zoom ×200, the three circles are added).

DESCRIPTION OF THE EMBODIMENTS

According to one subject, the invention relates to a nonwoven substrate comprising:

-   -   from 40% to 95% of wood fibers by weight relative to the total         weight of fibers of the substrate, and     -   from 5% to 60% of individualized bast fibers by weight relative         to the total weight of fibers of the substrate,         characterized in that the individualized bast fibers have,         relative to the dry weight of the individualized bast fibers, a         cellulose content greater than or equal to 80%, a hemicellulose         content less than or equal to 10%, and a lignin content less         than or equal to 9.5%.

For the purposes of the present application, the term “nonwoven substrate” denotes a manufactured sheet consisting of a web or ply of directionally or randomly oriented fibers bonded together by friction and/or cohesion, and/or adhesion, with the exception of paper and products obtained by weaving, knitting, tufting or stitching, which incorporate binding yarns or filaments or are felted by wet fulling, regardless of whether they are needle punched.

For the purposes of the present application, the term “bast fiber” denotes a plant fiber contained in the secondary phloem of plants.

By way of bast fiber, mention may be made of hemp fiber, Indian hemp fiber, jute fiber, kenaf fiber, kudzu fiber, coin vine fiber, flax fiber, okra fiber, nettle fiber, papyrus fiber, ramie fiber, sisal fiber, esparto fiber or mixtures thereof, in particular hemp fiber, flax fiber or a mixture thereof, most particularly flax fiber.

Typically, bast fibers are composed of cellulose, hemicellulose, lignin and other compounds such as pectins, proteins, waxes and inorganic compounds. For the purposes of the present application, the term “individualized bast fiber” denotes an elementary bast fiber of which the cellulose, hemicellulose and lignin content is greater than or equal to 98.5%, in particular 98.75%, most particularly 99%. The individualized bast fibers are obtained during a simple step of treating the bast fibers under pressure in a solvent.

Without wanting to be bound by any theory, the inventors are of the opinion that a simple treatment under pressure in a solvent makes it possible to dissolve the pectin cement in order to obtain the individualized bast fibers of the present invention which have specific cellulose, lignin and hemicellulose contents.

The treatment under pressure in a solvent also allows the individualized bast fibers of the present invention to have great flexibility. Advantageously, this great flexibility of the individualized bast fibers gives the nonwoven substrate of the invention its suppleness and its mechanical properties since the individualized bast fibers are well assembled.

Furthermore, these individualized bast fibers entangle with one another better than non-individualized bast fibers so that the nonwoven substrate of the invention is more pleasant to the touch, in particular is softer and less rough, than a substrate comprising non-individualized bast fibers.

The individualized bast fibers of the nonwoven substrate of the invention are characterized by specific cellulose, lignin and hemicellulose contents. In particular, the individualized bast fibers can have, relative to the dry weight of the individualized bast fibers:

-   -   a cellulose content between 80% and 98%, most particularly         between 89% and 97%,     -   a hemicellulose content between 0.5% and 10%, most particularly         between 1% and 5.5%, and     -   a lignin content between 1% and 9.5%, most particularly between         1.5% and 5%.

The cellulose, lignin and hemicellulose contents may depend on the nature of the bast fibers.

For example, individualized flax fibers can have, relative to the dry weight of the individualized flax fibers:

-   -   a cellulose content greater than or equal to 80%, in particular         between 85% and 98%, most particularly between 95 and 97%,     -   a hemicellulose content less than or equal to 9%, in particular         between 0.75% and 7.5%, most particularly between 1% and 3%, and     -   a lignin content less than or equal to 5%, in particular between         1% and 4%, most particularly between 1.5% and 2%.

Individualized hemp fibers can, for example, have, relative to the dry weight of the individualized hemp fibers:

-   -   a cellulose content greater than or equal to 80%, in particular         between 80% and 98%, most particularly between 89 and 93%,     -   a hemicellulose content less than or equal to 10%, in particular         between 0.5% and 10%, most particularly between 2% and 5.5%, and     -   a lignin content less than or equal to 10%, in particular         between 2.5% and 9%, most particularly between 3% and 5%.

The SCAN-CM 71 (2009) method will be used to determine the cellulose and hemicellulose content in the individualized fibers relative to the dry weight of the individualized bast fibers.

For the purposes of the present invention, the lignin content in the individualized fibers relative to the dry weight of the individualized bast fibers corresponds to the sum of the content of insoluble lignin and the content of soluble lignin, the content of insoluble lignin being determined according to the TAPPI 222 (2006) method and the content of soluble lignin being determined by the conventional method using UV spectrophotometry.

The individualized bast fibers can have a length between 1 mm and 150 mm, in particular between 1.5 mm and 100 mm, most particularly between 2 mm and 50 mm.

According to one embodiment, the individualized bast fibers can have a length between 4 mm and 20 mm, in particular between 6 mm and 15 mm, most particularly between 8 mm and 14 mm, even most particularly between 10 mm and 12 mm.

According to one alternative embodiment, the individualized bast fibers can have a length between 20 mm and 150 mm, in particular between 30 mm and 100 mm, most particularly between 35 mm and 50 mm.

According to another alternative embodiment, the individualized bast fibers can have a length between 1 mm and 10 mm, in particular between 1.5 mm and 8 mm, most particularly between 2 mm and 5 mm.

The bast fibers can be cut before the treatment under pressure so as to have a length included in the abovementioned ranges. The conventional cutting techniques that may be used are guillotine cutting of bast fibers, or grinding of the bast fibers with or without an air cyclone or sieve system for eliminating excessively short and excessively long fibers.

The bast fibers, in particular flax or hemp fibers, may also be “cottonized” bast fibers which are bast fibers that are modified so as to have a length in the above ranges and attenuated to pass through cotton spinning mills.

The amount of individualized bast fibers in the nonwoven substrate of the invention may, in particular, be from 10% to 50%, most particularly from 15% to 30% by weight relative to the total weight of fibers of the substrate.

The individualized bast fibers have specific characteristics; a subject of the invention is an individualized bast fiber as described above. The individualized bast fiber of the invention has, relative to its dry weight, a cellulose content greater than or equal to 80%, a hemicellulose content less than or equal to 10%, and a lignin content less than or equal to 9.5%.

Typically, the wood fibers originate from a hardwood pulp, a softwood pulp, or a mixture thereof, in particular a softwood pulp.

The amount of wood fibers in the nonwoven substrate of the invention may, in particular, be from 60% to 90%, most particularly from 80% to 85% by weight relative to the total weight of fibers of the substrate.

The nonwoven substrate of the invention may also comprise additional fibers chosen from lyocell fibers (cellulose fiber ground and dissolved in N-methylmorpholine N-oxide monohydrate, for the purpose of obtaining fibers with a cross section of variable shape (round, oval, cross-shaped, circular, lamellar cross section) with a calibrated linear density and length, that those skilled in the art can choose as a function of their requirements), viscose fibers (obtained by dissolving cellulose owing to the modification of its hydroxyl groups by carbon disulfide (CS₂), then its precipitation in the presence of sulfuric acid (H₂SO₄) for the purpose of obtaining fibers with a cross section of variable shape (round, oval, cross-shaped, circular, lamellar cross section) with calibrated linear density and length, that those skilled in the art can choose as a function of their requirements), cellulose acetate fibers, biodegradable polymer fibers and mixtures thereof, in particular lyocell fibers.

Advantageously, the lyocell fibers may increase the softness and the dry strength of the plant paper according to the invention.

For the purposes of the present application, “biodegradable polymer fiber” denotes a polymer fiber that a bacterial action, natural or induced, rapidly decomposes and makes it disappear from the environment by converting it into simple molecules that can be used by plants. Examples of biodegradable polymer fibers are polylactic acid (PLA) fibers, polyhydroxyalkanic acid (PHA) fibers and a mixture thereof. By way of polyhydroxyalkanic acid (PHA), mention may be made of poly(β-hydroxybutyrate) (PHB).

For example, the amount of additional fibers in the nonwoven substrate of the invention may be less than or equal to 15%, in particular from 1% to 10%, most particularly from 4% to 6% by weight relative to the total weight of fibers of the substrate.

Typically, the additional fibers may have a length greater than or equal to 1 mm, in particular from 4 mm to 20 mm, most particularly from 9 mm to 11 mm.

The additional fibers may have a fineness of from 0.5 dTex to 2.5 dTex, in particular from 1 dTex to 2 dTex, most particularly from 1.25 dTex to 1.75 dTex.

The additional fibers may also have a fineness of from 2.5 dTex to 30 dTex, in particular from 2.75 dTex to 10 dTex, most particularly from 3 dTex to 3.5 dTex.

According to one particular embodiment, the nonwoven substrate comprises:

-   -   from 75% to 85% of wood fibers by weight relative to the total         weight of fibers of the substrate,     -   from 15% to 20% of individualized bast fibers, in particular of         individualized flax fibers, by weight relative to the total         weight of fibers of the substrate,     -   from 4% to 6% of additional fibers, in particular of lyocell         fiber, by weight relative to the total weight of fibers of the         substrate,         in which the individualized bast fibers have, relative to the         dry weight of the individualized bast fibers, a cellulose         content of from 88% to 99%, a hemicellulose content of from 0.5%         to 6%, most particularly from 1% to 4%, and a lignin content of         from 1% to 4%, most particularly from 1.5% to 3%.

The nonwoven substrate of the invention may also comprise an additive normally used for paper production in order to develop or to confer on the substrate new properties such as, for example, chemical, optical, sensory or mechanical properties such as the dry strength, the wet strength and/or the folding resistance.

By way of additive, mention may be made of a wet strength agent, a dry strength agent, a softening agent, an active ingredient, a lotion composition, a wetting agent, latexes, or mixtures thereof, in particular a wet strength agent, a dry strength agent, an active ingredient, a lotion composition or mixtures thereof, most particularly a wet strength agent and an active ingredient.

For example, the amount of additive is less than 3% by weight of solids of the substrate, in particular from 0.5% to 2% by weight of solids of the substrate, most particularly from 1.3% to 1.7% by weight of solids of the substrate.

A wet strength agent makes it possible to reduce the potential degradation of the nonwoven substrate of the invention if the latter is brought into contact with a liquid, such as water. For example, the wet strength agent may be chosen from polyamides, such as an epichlorohydrin resin, a polyamine-epichlorohydrin resin, a polyamide-epichlorohydrin resin, a poly(aminoamide)-epichlorohydrin resin, a urea-formaldehyde resin, a melamine-formaldehyde resin, an alkyl-ketene dimer, alkylsuccinic anhydride, a polyvinylamine, an oxidized polysaccharide, and mixtures thereof.

A dry strength agent makes it possible to increase the strength of the nonwoven substrate of the invention if the latter is subjected to substantial mechanical stresses. The dry strength agent may be chosen from starches and modified gums, cellulose polymers, synthetic polymers such as, for example, carboxymethylcellulose, polyacrylamides, and mixtures thereof.

A softening agent makes it possible to improve the softness of the nonwoven substrate of the invention. Typically, a softening agent is a fatty acid, a siloxane compound, a silicone compound, an aminosilicone compound, an Aloe vera extract, a sweet almond extract, a chamomile extract, a quaternary ammonium compound, and mixtures thereof.

The active ingredient may be chosen from sebum regulators, mattifying agents, astringents, acidifying agents, healing agents, exfoliants or keratoregulators, occlusive agents, protective agents, emollients, nourishing agents, moisturizers, anti-aging agents, calmatives, decongestants or venotonics, UV-screening agents, hygroscopic agents, gelling agents, free-radical scavengers, cell-regenerating or cell-stimulating agents, firming agents, tightening agents, anti-glycation agents, lightening agents, or mixtures thereof.

By way of a biocidal compound, mention may be made of antimicrobial agents, antibacterial agents, disinfectants or mixtures thereof.

Examples of a decongestant are menthol extract and/or eucalyptus extract.

Vitamin E is an example of a moisturizer.

The humectant may be a sugar alcohol such as glycerol or sorbitol; a glycol, such as propylene glycol, butylene glycol, pentylene glycol or dipropylene glycol; or polyethylene glycol; or else mixtures thereof, in particular glycerol.

Advantageously, the humectant confers on the nonwoven substrate of the invention its conformability, its softness, its drape and its resistance to marking. Furthermore, the nonwoven substrate of the invention is advantageously capable of satisfactorily absorbing, retaining and releasing a cosmetic lotion.

Typically, the nonwoven substrate of the invention has a basis weight of from 15 g/m² to 90 g/m², in particular from 35 g/m² to 75 g/m².

Advantageously, a basis weight in these value ranges confers on the nonwoven substrate of the invention its conformability (ability of the nonwoven substrate of the invention to adopt the shape of the face of a user) and an absorption capacity and a release capacity that are satisfactory for cosmetic use.

The nonwoven substrate of the invention may also undergo additional treatments known to the papermaking industry, such as hydroentanglement treatment.

Thus, one embodiment of the invention is a nonwoven substrate as described above, in which the fibers are entangled.

The bulk of the nonwoven substrate in which the fibers are entangled is higher than the bulk of a nonwoven substrate in which the fibers are not entangled. Accordingly the nonwoven substrate in which the fibers are entangled is advantageously more pleasant to the touch, in particular softer and less rough, and has a higher absorption capacity.

By virtue of its properties, the nonwoven substrate of the invention can be used as a cosmetic wipe, a hygiene wipe, a cosmetic facial mask, or a household wipe.

According to one aspect, the present invention relates to a wipe comprising the nonwoven substrate of the invention, in particular a cosmetic wipe, a hygiene wipe or a household wipe.

The nonwoven substrate of the invention is produced according to a process comprising the following steps:

-   -   a) treating bast fibers under pressure in a solvent in order to         obtain the individualized bast fibers,     -   b) mixing the individualized bast fibers and wood fibers in         order to obtain a fiber mixture, and     -   c) producing a nonwoven substrate from the fiber mixture by the         wetlaid process, by the drylaid process or by the airlaid         process, in particular by the wetlaid process.

In the treatment step a) of the process of the invention, the bast fibers are mixed with the solvent, for example in a reactor operating under pressure, then this mixture is placed under pressure in order to obtain the individualized bast fibers. The individualized bast fibers are then separated from the solvent, for example by passing through a screw press or a centrifuge, in order to obtain, on the one hand, the individualized bast fibers and, on the other hand, the solvent.

The treatment step a) is carried out under pressure, i.e. at a pressure above atmospheric pressure, in particular at a pressure between 5 bar and 10 bar, more particularly between 7 bar and 8.5 bar. Advantageously, the pressure makes it possible to facilitate the individualization of the fibers.

According to one embodiment, the temperature of the solvent during step a) may be above ambient temperature. The temperature of the solvent may, for example, be between 50° C. and 250° C., in particular between 100° C. and 200° C., most particularly between 160° C. and 170° C.

The duration of the treatment step a) will depend on the bast fiber. Typically, this duration may be greater than or equal to 5 minutes, in particular greater than or equal to 60 minutes, most particularly from 120 minutes to 300 minutes.

According to one embodiment, the solvent is an aqueous solvent, most particularly the solvent is water.

During step a), the weight of solvent is typically greater than the dry weight of bast fibers. Thus, the ratio between the weight of solvent and the dry weight of bast fibers may be between 1.1 and 20, in particular between 2 and 10, more particularly between 2.5 and 3.5.

The treatment step a) of the process of the invention may be an alkaline treatment or an acid treatment, in particular an alkaline treatment.

The solvent may comprise an additive such as an acid or a base.

The acid may be a bisulfite such as sodium bisulfite or calcium bisulfite.

The base may be calcium sulfite, calcium carbonate, sodium hydroxide, sodium sulfite, sodium carbonate, a mixture of sodium hydroxide and anthraquinone, or mixtures thereof, in particular sodium hydroxide or a mixture of sodium sulfite and sodium carbonate.

The weight concentration of additive in the solvent depends on the additive. For example, the concentration of a mixture of sodium sulfite and sodium carbonate may be from 1% to 20% of sodium sulfite and from 0.25% to 10% of sodium carbonate, in particular from 2% to 8% of sodium sulfite and from 0.8% to 3% of sodium carbonate. The weight concentration of sodium hydroxide in the solvent may, for example, be between 0.5 and 20%, in particular between 1% and 15%, most particularly between 2% and 7%, even more particularly between 5.5% and 6.5%.

According to a first particular variant, the treatment step a) is carried out at a solvent temperature between 165° C. and 170° C., at a pressure between 8 bar and 8.5 bar, for a period of from 110 minutes to 120 minutes, the solvent being water comprising a mixture of sodium sulfite and sodium carbonate, the sodium sulfite concentration in the solvent being between 2% and 8% and the sodium carbonate concentration in the solvent being between 0.8% and 3%.

According to a second particular variant, the treatment step a) is carried out at a solvent temperature between 160° C. and 165° C., at a pressure between 6.5 bar and 7.5 bar, for a period of from 170 minutes to 190 minutes, the solvent being water comprising sodium hydroxide, the sodium hydroxide concentration in the water being between 1% and 10%, in particular between 5.5% and 6.5%.

The bast fibers may undergo, before the treatment step a) of the process of the invention, a pretreatment step such as a retting.

Before the treatment step a), the bast fibers may undergo a cutting step a1) in order to obtain cut bast fibers, the length of which is between 1 mm and 150 mm, in particular between 1.5 mm and 100 mm, most particularly between 2 mm and 50 mm.

According to one embodiment, the cut bast fibers may have a length between 4 mm and 20 mm, in particular between 6 mm and 15 mm, most particularly between 10 mm and 12 mm.

According to one alternative embodiment, the cut bast fibers may have a length between 20 mm and 150 mm, in particular between 30 mm and 100 mm, most particularly between 35 mm and 50 mm.

According to one alternative embodiment, the cut bast fibers may have a length between 1 mm and 10 mm, in particular between 1.5 mm and 8 mm, most particularly between 2 mm and 5 mm.

The cutting step a1) can be carried out by conventional techniques such as guillotine cutting, or grinding of the bast fibers with or without an air cyclone or sieve system for eliminating excessively short and excessively long fibers.

The bast fibers used in the mixing step b) of the process of the invention, in particular the flax or hemp fibers, may also be “cottonized” bast fibers which are bast fibers that are modified so as to have a length in the above ranges and attenuated to pass through cotton spinning mills.

The individualized bast fibers can subsequently undergo a washing step, for example in water, optionally followed by a drying step.

The additional fibers can, for example, be added to the individualized bast fibers and to the wood fibers during the mixing step b) in order to obtain the fiber mixture.

Step c) can implement a conventional wetlaid process for producing paper, in particular a wetlaid process involving an inclined table. Those skilled in the art will know how to adjust the parameters of the wetlaid process in order to produce the nonwoven substrate.

The wetlaid process is particularly suitable for individualized bast fibers having a length between 4 mm and 20 mm, in particular between 6 mm and 15 mm, most particularly between 10 mm and 12 mm.

The drylaid process is particularly suitable for individualized bast fibers having a length between 20 mm and 150 mm, in particular between 30 mm and 100 mm, most particularly between 35 mm and 50 mm.

The airlaid process is, for its part, particularly suitable for individualized bast fibers having a length between 1 mm and 10 mm, in particular between 1.5 mm and 8 mm, most particularly between 2 mm and 5 mm.

Step c) can alternatively implement a drylaid or airlaid process for producing paper. The drylaid or airlaid process makes it possible, typically, to form a web which can then undergo a consolidation step to form the nonwoven substrate of the invention. Advantageously, the consolidation step makes it possible to improve the cohesion of the fibers and therefore to consolidate the structure of the nonwoven substrate of the invention. By way of consolidation technique, mention may be made of mechanical consolidation, thermal consolidation, chemical consolidation and mixtures thereof, in particular mechanical consolidation.

The individualized bast fibers which undergo the step c) for drylaid or airlaid production of paper can undergo, before step b), a drying step b1).

The drying step b1) can be carried out at a temperature between 50° C. and 120° C., in particular between 60° C. and 90° C. A temperature in these ranges advantageously makes it possible to minimize the duration of this drying step b1) while at the same time minimizing the deterioration of the fibers, thus optimizing the process of the invention. Advantageously, this drying step b1) makes it possible to limit, or even avoid, the agglomeration of the dried individualized bast fibers. Thus, the process of the invention does not require a long and expensive step of deagglomeration of the fibers. The drying step b1) can for example be carried out in a tunnel, in a rotary air drier, or by winding the fibers and through-air drying. Advantageously, and contrary to conventional drying by means of a drying roll, these drying techniques also make it possible to minimize, or even limit, the agglomeration of the dried individualized bast fibers.

The nonwoven substrate produced during step c) may undergo a entanglement treatment in order to prepare the nonwoven substrate in which the fibers are entangled.

Thus, one aspect of the invention is a process for preparing a nonwoven substrate in which the fibers are entangled, the process comprising a step in which the nonwoven substrate produced during step c) of the process according to the invention undergoes an entanglement treatment step d) such as mechanical consolidation, thermal consolidation, chemical consolidation or mixtures thereof, in particular mechanical consolidation, chemical consolidation or mixture thereof, most particularly mechanical consolidation eventually followed by chemical consolidation.

Thermal consolidation uses the properties of thermoplasticity of synthetic fibers to entangle the fibers of the nonwoven substrate.

Chemical consolidation consists in coating a binder in solution such as cationic starch or a latex of styrene butadiene rubber to entangle the fibers of the nonwoven substrate.

Mechanical consolidation consists of a physical entanglement of the fibers of the nonwoven substrate. Examples of mechanical consolidation are needlepunching and hydroentanglement, in particular hydroentanglement.

According to a specific embodiment, the entanglement treatment of step d) is a hydroentanglement treatment.

Typically, a hydroentanglement treatment uses water jets under a pressure that may, for example, be between 20 bar and 800 bar, in order to entangle the fibers of the nonwoven substrate. The nonwoven substrate circulates over one or more tables or is conveyed from roller to roller, installed on the surface of which are injectors that inject the pressurized water. The water jets are generated when the pressurized water passes through a strip perforated with holes or nozzles having, for example, a diameter of from 80 μm to 150 μm, arranged in a proportion of 1 to 3 holes per millimeter, over one or more rows typically 3 mm to 5 mm apart. Typically, the water pressure can increase from the first to the last injectors. These very fine water jets penetrate the nonwoven substrate and rebound off the table or the roller, or off an intermediate belt, in a three-dimensional manner in order to entangle the fibers with one another. The two sides of the nonwoven substrate can undergo this hydroentanglement treatment one or more times. In order to avoid inundating the nonwoven substrate, suction boxes may be installed under the table(s) or inside the rollers. The residual water sucked up by the suction boxes can then be recycled and cleaned of any impurity in order to be reused. The nonwoven substrate thus consolidated can then be dried by drying rolls, a tunnel, or through-air drying rolls.

Advantageously, the sensory properties, in particular the softness, and the absorption capacity of the nonwoven substrate of the invention that has undergone a hydroentanglement treatment are improved. Moreover, the nonwoven substrate of the invention that has undergone a hydroentanglement treatment can form harmonious folds when it is suspended, it has a greater tensile strength, and is easily shaped. Due to the improvement in its sensory properties, and in particular in its softness and in its conformability, the nonwoven substrate of the invention that has undergone the hydroentanglement treatment can also, and advantageously, be used as a substrate for a cosmetic product and hygiene product previously described.

Typically, the additive may be added to the fiber mixture before, during or after step c) or after step d). For example, the additive may be added after step c) or after step d), by means of a size press, of coating or of spraying. In particular, the wet strength agent may be added to the fiber mixture before said mixture undergoes step c) in order to improve the interaction between the wet strength agent and the wood fibers.

Typically, after step c) or after step d), the nonwoven substrate of the invention can be dried by a drying device, such as drying rolls, through-air rolls, or a tunnel.

The nonwoven substrate of the invention may also undergo additional treatments known to the papermaking industry. Typically, one of these treatments allows the production of a multilayer nonwoven substrate using multiple head boxes.

The nonwoven substrate of the invention may also undergo a cutting step e) in order to produce a wipe as described above.

Thus, one aspect of the invention is a process for preparing a wipe, comprising a step e) of cutting the nonwoven substrate prepared by the process according to the invention or the nonwoven substrate in which the fibers are entangled, prepared by the process according to the invention.

This cutting step e) is a conventional step. Those skilled in the art will know how to adjust it in order to obtain the desired wipe.

EXAMPLES Example 1: Bast Fibers Individualized by the Process According to the Invention Example 1.1: The Treatment of the Flax Fibers is Carried Out at a Pressure of 7 Bar, a Temperature of 164° C.; the Solvent is Pure Water

Individualized flax fibers are obtained according to the following treatment under pressure:

Flax fibers are cut so that the flax fibers have a length of 8 mm. The cut flax fibers and the solvent, i.e. water, are mixed in a reactor operating under pressure and under a temperature so that the ratio between the dry weight of flax fibers and the volume of water is 0.33. The solvent/fiber mixture is heated to 164° C. over the course of 26 minutes and the pressure in the reactor is increased to 7 bar. The temperature of 164° C. and the pressure of 7 bar are maintained for 120 minutes. After this treatment, the flax fibers are separated from the solvent, washed with water for 60 minutes, centrifuged and, finally, dried at 105° C. for 16 h.

Example 1.2: The Treatment of the Flax Fibers is Carried Out at a Pressure of 7 Bar, a Temperature of 164° C.; the Solvent Comprises Water and 6% of Sodium Hydroxide

The treatment under pressure that makes it possible to obtain the individualized flax fibers is similar to that described in Example 1-1, the differences being that the solvent comprises water and 6% of sodium hydroxide and that the solvent/fiber mixture is heated to 164° C. over the course of 15 minutes.

Example 1.3: The Treatment of the Flax Fibers is Carried Out at a Pressure of 7 Bar, a Temperature of 164° C.; the Solvent Comprises Water and 2% of Sodium Hydroxide

The treatment under pressure that makes it possible to obtain the individualized flax fibers is similar to that described in Example 1-1, the differences being that the solvent comprises water and 2% of sodium hydroxide and that the solvent/fiber mixture is heated to 164° C. over the course of 22 minutes.

Example 1.4: The Treatment of the Flax Fibers is Carried Out at a Pressure of 8.2 Bar, a Temperature of 170° C.; the Solvent Comprises Water, 7.5% of Sodium Sulfite and 2.5% of Sodium Carbonate

Individualized flax fibers are obtained according to the following treatment under pressure:

Flax fibers are cut so that the flax fibers of the bundles have a length of 8 mm. The cut flax fibers and the solvent, i.e. water, 7.5% of sodium sulfite and 2.5% of sodium carbonate, are mixed in a reactor operating under pressure and under a temperature such that the ratio between the dry weight of flax fibers and the volume of water is 0.33. The solvent/fiber mixture is heated to 170° C. over the course of 7 minutes and the pressure in the reactor is increased to 8.2 bar. The temperature of 170° C. and the pressure of 8.3 bar are maintained for 180 minutes. After this treatment, the flax fibers are separated from the solvent, washed with water for 60 minutes, centrifuged and, finally, dried at 105° C. for 16 h.

The cellulose, hemicellulose and lignin contents of the flax fibers which have undergone this treatment under pressure are indicated in Table 1.

Example 1.5: The Treatment of the Flax Fibers is Carried Out at a Pressure of 8.2 Bar, a Temperature of 170° C.; the Solvent Comprises Water, 2.5% of Sodium Sulfite and 0.83% of Sodium Carbonate

The treatment under pressure that makes it possible to obtain the individualized flax fibers is similar to that described in Example 1-4, the differences being that the solvent comprises water, 2.5% of sodium sulfite and 0.83% of sodium carbonate, that the solvent/fiber mixture is heated to 170° C. over the course of 14 minutes, and that the pressure is 8.5 bar.

Example 1.6: The Treatment of the Hemp Fibers is Carried Out at a Pressure of 7 Bar, a Temperature of 164° C.; the Solvent is Pure Water

The protocol is similar to that described in Example 1.1, the difference being that the flax fibers are replaced by the hemp fibers.

Example 1.7: The Treatment of the Hemp Fibers is Carried Out at a Pressure of 8.2 Bar, a Temperature of 170° C.; the Solvent Comprises Water 7.5% of Sodium Sulfite and 2.5% of Sodium Carbonate

The protocol is similar to that described in Example 1.4, the difference being that the flax fibers are replaced by the hemp fibers.

Example 1.Comparative: Flax Fibers that have not Undergone Treatment Under Pressure

In this Example 1.comparative, flax fibers undergo the following treatment: Flax fibers are cut so that the flax fibers of the bundles have a length of 8 mm. The cut flax fibers and the solvent, i.e. water, are mixed in a reactor operating under a temperature so that the ratio between the dry weight of flax fibers and the volume of water is 0.05. The solvent/fiber mixture is heated to 70° C. and the pressure is atmospheric pressure. The temperature of 70° C. is maintained for 20 minutes. After this treatment, the flax fibers are separated from the solvent and dried at 80° C. for 16 h.

Example 2: Characterization of the Flax Fibers Obtained During Examples 1.1 to 1.5 and Example 1.Comparative Example 2.1: Cellulose, Hemicellulose and Lignin Contents in the Flax Fibers

The cellulose and hemicellulose content in the flax fibers is determined according to the SCAN-CM 71 method mentioned above.

The lignin content in the flax fibers is determined as mentioned above.

The cellulose, hemicellulose and lignin contents of the flax fibers that have undergone the treatments of Examples 1.1 to 1.5 and of Example 1.comparative are indicated in Table 1.

TABLE 1 Cellulose Lignin Hemicellulose content (%) content (%) content (%) Example 1.1 89.8 3.9 5.3 Example 1.2 96.4 1.9 1.1 Example 1.3 93.2 2.9 3.3 Example 1.4 95.2 1.5 2.7 Example 1.5 93.1 2.3 4.0 Example 78.4 4.4 9.5 1.comparative

Table 1 demonstrates that the flax fibers that have undergone the treatment under pressure have, relative to the dry weight of said flax fibers, the particular cellulose, lignin and hemicellulose contents of the individualized flax fibers of the invention. The flax fibers obtained in Example 1.comparative have, according to Table 1, a cellulose content below 80%, i.e. outside the particular cellulose content of the individualized flax fibers of the invention.

Example 2.2: Optical Microscopy Observation of the Flax Fibers

The flax fibers obtained in Examples 1-1 to 1-5 and in Example 1.comparative are pulped for 3 minutes at a concentration of 3 g/L and then kept in suspension for 20 minutes.

The flax fibers thus treated are then observed by optical microscopy.

FIGS. 1 to 6 show the optical microscopy images of the fibers.

FIGS. 1 to 5 demonstrate that the flax fibers obtained in Examples 1-1 to 1-5 are individualized; indeed, no fiber bundle is visible in FIGS. 1 to 5 . Furthermore, FIGS. 1 to 5 show that these individualized flax fibers are flexible since they are curved.

Conversely, several flax fiber bundles are visible in FIG. 6 . This FIG. 6 thus illustrates that the flax fibers obtained in Example 1.comparative are not individualized. Furthermore, these flax fibers are not flexible since they are grouped together to form bundles.

Example 3: Entangled Nonwoven Substrate According to the Invention Example 3.1: Substrate Comprising 15% of Flax Fibers Obtained in Example 1.1, 5% of Lyocell Fibers and 80% of Wood Fibers

The flax fibers obtained in Example 1.1, wood fibers (Sodra Black 85Z) and lyocell fibers (10 mm, 1.7 dTex) are mixed in order to obtain a fiber mixture. The fiber mixture then passes over a draining gauze in order to obtain a nonwoven substrate.

This nonwoven substrate then undergoes a hydroentanglement treatment by passing under two injection rails, with strips comprising two rows, each one at a pressure of 20 bar.

The nonwoven substrate has a basis weight of 60 g/m².

Example 3.2: Substrate Comprising 15% of Flax Fibers Obtained in Example 1.2, 5% of Lyocell Fibers and 80% of Wood Fibers

The protocol is similar to that described in Example 3.1, the difference being that the flax fibers obtained in Example 1.1 are replaced with flax fibers obtained in Example 1.2.

The nonwoven substrate has a basis weight of 60 g/m².

Example 3.3: Substrate Comprising 15% of Flax Fibers Obtained in Example 1.4, 5% of Lyocell Fibers and 80% of Wood Fibers

The protocol is similar to that described in Example 3.1, the difference being that the flax fibers obtained in Example 1.1 are replaced with flax fibers obtained in Example 1.4.

The nonwoven substrate has a basis weight of 60 g/m².

Example 3.4: Substrate Comprising 20% of Flax Fibers Obtained in Example 1.4 and 80% of Wood Fibers

The protocol is similar to that described in Example 3.1, the differences being that the flax fibers obtained in Example 1.1 are replaced with flax fibers obtained in Example 1.4 and no Lyocell fibers are added.

The nonwoven substrate has a basis weight of 60 g/m².

Example 3.5: Substrate Comprising 50% of Flax Fibers Obtained in Example 1.4, 5% of Lyocell Fibers and 45% of Wood Fibers

The protocol is similar to that described in Example 3.1, the difference being that the flax fibers obtained in Example 1.1 are replaced with flax fibers obtained in Example 1.4.

The nonwoven substrate has a basis weight of 60 g/m².

Example 3.6: Substrate Comprising 55% of Flax Fibers Obtained in Example 1.4 and 45% of Wood Fibers

The protocol is similar to that described in Example 3.1, the differences being that the flax fibers obtained in Example 1.1 are replaced with flax fibers obtained in Example 1.4 and no Lyocell fibers are added.

The nonwoven substrate has a basis weight of 60 g/m².

Example 3.7: Substrate Comprising 20% of Hemp Fibers Obtained in Example 1.6 and 80% of Wood Fibers

The protocol is similar to that described in Example 3.1, the difference being that the flax fibers obtained in Example 1.1 are replaced with hemp fibers obtained in Example 1.6 and no Lyocell fibers are added.

The nonwoven substrate has a basis weight of 60 g/m².

Example 3.8: Substrate Comprising 20% of Hemp Fibers Obtained in Example 1.7 and 80% of Wood Fibers

The protocol is similar to that described in Example 3.1, the difference being that the flax fibers obtained in Example 1.1 are replaced with hemp fibers obtained in Example 1.7 and no Lyocell fibers are added.

The nonwoven substrate has a basis weight of 60 g/m².

Example 3.Comparative: Substrate Comprising 15% of Flax Fibers Obtained in Example 1.Comparative, 5% of Lyocell Fibers and 80% of Wood Fibers

The protocol is similar to that described in Example 3.1, the difference being that the flax fibers obtained in Example 1.1 are replaced with flax fibers obtained in Example 1.comparative.

The nonwoven substrate has a basis weight of 60 g/m².

Example 4: Characterization of the Substrates of Examples 3.1 to 3.8, of Example 3.Comparative, and of a Control Substrate Example 4.1: Dry Tensile Strength

The dry tensile strength is determined for the substrates of the Examples 3.1 to 3.8 and is compared to that of a control substrate comprising 20% of lyocell fibers and 80% of wood fibers (Sodra Black 85Z) and to the substrate of Example 3.Comparative.

The dry tensile strength is determined according to the EN 29073-3 method (1992).

The results, presented in FIG. 7 , demonstrate that all the substrates have a dry tensile strength of the same order of magnitude, whatever the content of individualized bast fibers and whatever the nature of the bast fibers.

Example 4.2: Wet Tensile Strengths

The wet tensile strength is determined according to the ISO 12625-5 method (2017) for the substrates of the Examples 3.1 and 3.3 to 3.8 and is compared to that of the control substrate comprising 20% of lyocell fibers and 80% of wood fibers (Sodra Black 85Z) and the substrate of Example 3.Comparative.

The wet tensile strengths of all substrates are satisfactory and are of the same order of magnitude, whatever the content of individualized bast fibers and whatever the nature of the bast fibers.

Example 4.3: Deformation

The deformation is determined for the four substrates of the examples and the control substrate.

The deformation is determined according to the EN 29073-3 method (1992).

The results, presented in FIG. 8 , demonstrate that all the substrates have a deformation of the same order of magnitude.

Example 4.4: Optical Microscopy Observation of the Substrates of Example 3.3 and Example 3.Comparative

FIGS. 9 and 10 show the respective optical microscopy images of the substrate of Example 3.3 and the substrate of Example 3.comparative (optical zoom ×200).

FIG. 9 demonstrates that the substrate of Example 3.3 does not comprise any flax fiber bundles. Flax fiber bundles are, on the other hand, visible in the substrate of Example 3.comparative (in the circles of FIG. 10 ).

Furthermore, the fibers of the substrate of Example 3.3 show better entanglement than the fibers of the substrate of Example 3.comparative.

These results are characteristic of the individualization and of the flexibility of the flax fibers of the substrate of Example 3.3.

Example 4.5: Sensory Evaluation of the Substrates of Examples 3.1 to 3.3, 3.7, 3.8 and of Example 3.Comparative

The sensory properties of the substrates of Examples 3.1 to 3.3, 3.7, 3.8 and of Example 3.comparative are evaluated by cosmetic panels that are organized with several panelists.

For each substrate, each panelist judges the softness, the color, the tear strength and the unfolding ability.

The substrates of Examples 3.1 to 3.3, 3.7 and 3.8 are soft to the touch and are quite natural in color, the softest being the substrate of Example 3.3.

The substrate of Example 3.comparative is not soft since small particles, corresponding to the fiber bundles, are visible.

The substrates of Examples 3.1, 3.3, 3.7, 3.8 and of Example 3.comparative do not tear apart when they are subjected to manual tearing.

All the substrates tested unfold well. 

1. Nonwoven substrate comprising: from 40% to 95% of wood fibers by weight relative to the total weight of fibers of the substrate, and from 5% to 60% of individualized bast fibers by weight relative to the total weight of fibers of the substrate, characterized in that the individualized bast fibers have, relative to the dry weight of the individualized bast fibers, a cellulose content greater than or equal to 80%, a hemicellulose content less than or equal to 10%, and a lignin content less than or equal to 9.5%.
 2. Nonwoven substrate according to claim 1, in which the bast fibers are chosen from hemp fiber, Indian hemp fiber, jute fiber, kenaf fiber, kudzu fiber, coin vine fiber, flax fiber, okra fiber, nettle fiber, papyrus fiber, ramie fiber, sisal fiber, esparto fiber and mixtures thereof.
 3. Nonwoven substrate according to claim 1 comprising additional fibers chosen from lyocell fibers, viscose fibers, cellulose acetate fibers, biodegradable polymer fibers and mixtures thereof.
 4. Nonwoven substrate according to claim 3, in which the amount of additional fibers is less than or equal to 15% by weight relative to the total weight of fibers of the substrate.
 5. Nonwoven substrate according to claim 1, in which the fibers are entangled.
 6. Wipe comprising the substrate as defined in claim
 1. 7. Process for producing a nonwoven substrate as defined in claim 1, comprising the following steps: a) treating bast fibers under pressure in a solvent in order to obtain the individualized bast fibers, b) mixing the individualized bast fibers and wood fibers in order to obtain a fiber mixture, and c) producing a nonwoven substrate from the fiber mixture by a wetlaid process, by a drylaid process or by an airlaid process.
 8. Process according to claim 7, in which the treatment step a) is carried out at a pressure between 5 bar and 10 bar.
 9. Process according to claim 7, in which the temperature of the solvent during the treatment step a) is between 50° C. and 250° C.
 10. Process according to claim 7, in which the solvent is an aqueous solvent.
 11. Process according to claim 7, in which the solvent comprises an additive.
 12. Process according to claim 11, in which the additive is an acid or a base.
 13. Process for producing a nonwoven substrate as defined in claim 7, in which the nonwoven substrate produced during step c) of the process undergoes an entanglement treatment step d).
 14. Process for producing a wipe, comprising a step e) of cutting the substrate produced by the process according to claim
 7. 